Physical Review C

Optical potentials model scattering off complex nuclear targets, but are typically phenomenological in nature. Here a widely used parameterization for nonlocal potentials, the Perey-Buck ansatz, is linked with calculations using first-principles forces. This provides insight into the success of Perey-Buck, as well as important lessons on its limitations.

Nucleon-adding and -removing transfer reactions provide a unique experimental window into the anatomy of the shell-model picture of atomic nuclei. The authors put the neutron-removing transfer reaction 47K(d,t) and the neutron-adding counterpart 47K(d,p) to work for meticulously probing our understanding of the neutron shell structure and interaction of the last valence proton in 46K. With that, they provided a unique benchmark for the nuclear shell model on the quest to describe shell evolution in neutron-rich nuclei.

Fission is a highly dissipative process. Stochastic methods like Brownian shape motion and Langevin dynamics couple macroscopic-microscopic models with dynamics. This paper compares and contrasts these two approaches within a consistent framework and demonstrates the connections between them. The work also hints at the potential role of higher-dimensional deformation modes in broadening the widths of the fission fragment mass yields to better match the measured yields.

A new capability of describing charge-exchange and transfer reactions by coupling different mass/charge partitions of the compound nucleus was developed within $ab$ $initio$ nuclear theory. We apply this capability to ${}^7$Li, employing the no-core shell model with continuum for the first time in a calculation that couples three mass/charge partitions, namely ${}^4$He + ${}^3$H, ${}^6$Li + n, and ${}^6$He + p, using a chiral nucleon-nucleon interaction as input. Specifically, we investigate the effect of interpartition coupling on the spectrum of ${}^7$Li and calculate cross sections for the ${}^6$Li(n,p)${}^6$He, ${}^6$He(p,n)${}^6$Li, and ${}^6$He(p,t)${}^4$He reactions. The results show that coupling the relevant mass/charge partitions is important for a consistent description of the ${}^7$Li spectrum and reaction cross sections, and offers a useful framework for interpreting existing data and guiding future measurements. This work also paves the way for calculations of transfer reactions relevant for fusion energy generation such as ${}^6$Li(n,t)${}^4$He.

The imbalance between matter and antimatter in our Universe remains one of the great mysteries of modern physics. The neutron’s electric dipole moment (EDM) is a sensitive probe of new sources of CP violation that could help explain this asymmetry. Searches for an EDM rely on extraordinarily precise measurements of the neutron spin precession, using polarized mercury atoms to monitor the applied magnetic field. But the mercury atoms themselves can interact with neutrons in a way that produces a tiny, spin-dependent frequency shift, potentially mimicking an EDM signal. In this study, the nEDM Collaboration, with the experiment based at the Paul Scherrer Institute, directly investigates this subtle neutron-mercury interaction. The results provide a precise characterization of an important systematic effect, improving the control of a key source of uncertainty in EDM measurements.

The Gerasimov-Drell-Hearn (GDH) sum rule establishes a fundamental link between the total absorption cross section of circularly polarized photons on longitudinally polarized nucleons and nuclei and their static properties. The two relative spin configurations, parallel or antiparallel, determine the absorption cross sections, ${\sigma }_P$ and ${\sigma }_A$. The sum rule relates the difference of the cross sections ($\mathrm{\Delta }\sigma )$ to the mass, spin, and anomalous magnetic moment of the nucleon (nucleus). It implies that a non-zero anomalous magnetic moment is connected to the excitation spectrum of the nucleon (nucleus) and, therefore, to its composite nature. Thus, measuring the GDH sum rule integral for different nuclear targets is a sensitive tool for studying both the nucleon resonance properties and the modifications of nucleon properties inside the nuclear medium. We present new precise data on the helicity-dependent total inclusive photoabsorption cross section for the proton and the deuteron, verifying the validity of the GDH sum rule. These new data provide a precise experimental benchmark for theoretical models of nucleons, both free and embedded in the nuclear medium.

There is much interest and activity in identifying transuranium isotopes and determining their cosmological origins, such as neutron star mergers. This paper studies how one could determine the production of transuranium isotopes in pulse nucleosynthesis based on isotopic yield ratios, a process that is very dependent on neutron fluence. The relationship between the neutron flux and abundances is determined in a rather unique way: by looking at yields from nuclear tests conducted during the Plowshares program. Making use of these nuclear tests (indicated in the figure) may help determine whether the periodic table has been extended in natural events in space.

We have constructed a quark-based nuclear model that extends from low densities into the crossover region where nucleonic matter begins to evolve into quark matter. It combines the quark-meson coupling model with the dual quarkyonic picture. A relativistic treatment of quark wave functions within nucleons ensures that quarkyonic matter emerges above nuclear saturation density, preserving consistency with conventional low-energy nuclear physics. Nuclear interactions are crucial for quantitative predictions in the quarkyonic regime. The predicted sound speed exhibits a pronounced peak and is consistent with constraints inferred from neutron-star observations using neural networks and Bayesian inference. The calculated pressures in symmetric nuclear matter and pure neutron matter also lie within the ranges inferred from high-energy heavy-ion collisions. This framework can help address the hyperon puzzle in massive neutron stars.

Where do the heavy elements in our universe come from, and how accurately can we model their creation? Accurately predicting the abundances of elements produced in the weak rapid neutron-capture ($r$- process) requires rigorous quantification of nuclear reaction uncertainties far from stability. This work utilizes cross sections with uncertainty-quantified optical potential and considers both independent (uncorrelated) rate variations and rate variations fully correlated via the underlying optical potential. While fully correlated variations alter the covariance structure among elemental yields, they do not automatically reduce the overall uncertainty envelope. By identifying specific neutron capture rates that have the most leverage on the $r$-process element production, this work provides a roadmap for experimental and theoretical efforts to constrain key nuclear reaction rates.

High-precision measurements of nuclear decay energies can reveal rare low-Q transitions with enhanced sensitivity to the absolute neutrino mass. Using the JYFLTRAP double Penning trap and the PI-ICR technique, the electron-capture Q value of ${}^{113}$Sn was determined with an eightfold improvement in precision over the previous evaluation. Combining the new mass result with known excited states in ${}^{113}$In identifies two energetically allowed low-Q electron-capture branches. In particular, an allowed transition to the 1029.650-keV state has $Q{*}_{EC}=9.60(20)$ keV and lies close to the L-shell binding energies. Atomic and nuclear calculations show enhanced spectral sensitivity near the endpoint, making this decay an interesting complementary system for future direct neutrino-mass studies.

Photons and dileptons produced in high energy nuclear collisions contain undistorted information about the conditions at their point of emission, such as the local temperature, flow velocity, and chemical potential. Using state of the art modeling of the collision dynamics, which reproduce hadronic spectra, the authors find good agreement with measurements by the STAR Collaboration at the Relativistic Heavy Collider, but differ from measurements by the PHENIX Collaboration in terms of magnitude but not shape. This work shows that the multimessenger approach to heavy-ion collisions previously used at higher energy is amenable to baryon-rich environments at lower temperatures, and paves the way for more comprehensive studies of the QCD phase diagram.

We have demonstrated a new way to reveal the electrical ‘fingerprint’ left by a single nuclear decay. When a radioactive atom implanted just beneath a surface decays, its products can eject a shower of secondary electrons from the surrounding material. Often undetected by conventional laboratory instruments, these electrons can create a substantial background in experiments that rely on precise electron counting. To study this process, we use a microscopic glass sphere suspended by laser light as a highly isolated charge detector with sub-electron charge sensitivity. We pair the sphere with a conventional scintillation detector that records the emitted radiation. By matching the timing of the two signals, we can link each charge change to a specific decay. We found that one alpha decay can knock more than 100 electrons from a material’s surface, while beta decays release far fewer. Measuring these electrical fingerprints one decay at a time could help experiments searching for rare events, including future sterile neutrino searches, to distinguish genuine signals from electrons released by radioactive impurities near detector surfaces.

Spin utilization in large particle accelerators is a young quantum technology, with practical realization only emerging in the late twentieth century. Polarized ion beams at the future Electron Ion Collider (EIC) are essential to address some of the most important open questions at the twenty-first-century frontiers of our understanding of the fundamental structure of matter. How does the proton spin of $1/2$ arise from the highly relativistic constituent quarks and gluons and their interactions via QCD? Are the quark and gluon nucleon spin distributions modified inside the nucleus? Can exotic gluons exist in the nucleus? Beyond these questions, polarized electron and ion beams are crucial for unravelling the full three-dimensional structure of the nucleon and of nuclei. This Perspective paper summarizes the science case and identifies polarized ion beams as the critical technology enabling the experiments that address these questions. The authors further discuss the required ion polarimetry and spin manipulation at the EIC, and identify a significant R&D effort, involving both national laboratories and universities, that will be required over roughly a decade to realize the polarized ion beams.